These studies will investigate relationships between reinforcing properties and subjective or mood-altering effects of drugs in normal volunteers. Reinforcing properties will be measured using a preference procedure in which subjects sample drug and a placebo under double blind conditions, and then choose between them. Mood states are evaluated using self-report questionnaires completed by subjects before and at regular intervals after drug ingestion. Two studies will investigate subject characteristics hypothesized to influence drug response, and one study will explore the effect of an environmental manipulation. One study will investigate whether a stable subject trait, genetic predisposition to alcoholism because of a positive family history of alcoholism, influences the subjective and/or reinforcing effects of alcohol and diazepam. Another study will explore the effects of the state of food deprivation on subjective and behavioral responses to amphetamine and diazepam. The third study will determine whether characteristics of the drug-taking environment alter subjects' responses to diazepam. We will relate the findings of these studies to the identification of possible risk factors for drug dependence.